# cross ratio

noun, Geometry
1.
a ratio relating four points in the real or complex plane.
Also called anharmonic ratio.
Origin of cross ratio
1880-1885
1880-85
Related forms
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
Cite This Source
Examples from the Web for cross-ratio
Historical Examples
• Before we draw conclusions from this result, we must investigate the meaning of a cross-ratio somewhat more fully.

• If we take the points in a different order, the value of the cross-ratio will change.

• The cross-ratio of four points equals that of the four conjugate points.

• If this cross-ratio equals −1 the four points are said to be four harmonic points.

• It is convenient to let the point at infinity occupy the last place in the symbolic expression for the cross-ratio.

• If this cross-ratio equals −1 the four tangents are said to be four harmonic tangents.

• We know that the cross-ratio of four points is equal to that of the corresponding row.

• The cross-ratio of any four points in one equals that of the corresponding points in the other.

### Difficulty index for cross ratio

Few English speakers likely know this word

### Word Value for cross

7
8
Scrabble Words With Friends